Apparatus for measuring the moisture content of moving materials

Abstract

Moisture in wood veneer strips received from a drying oven is measured by passing the veneer strips on a conveyor between arrays of conducting elements including a pair of transmitting bars on one side of the veneer and a pair of receiving plates juxtaposed therewith on the other. The transmitting bars are energized with signals out of phase with respect to each other on either side of ground, and the receiving plates are likewise disposed to receive the phased signals. When wet veneer passes between the plates arrays, part of the transmitted signal is shunted through the veneer, reducing the signal received by the receiving plates.

I claim: 
     
       1. Apparatus for measuring moisture content of moving material, said apparatus comprising: means for generating an alternating electrical signal;   first conductor means disposed in facing relation to a first side of said moving material for transmitting the alternating electrical signal;   second conductor means disposed in facing relation to the first side of said moving material in laterally spaced relation to said first conductor means for transmitting the alternating electrical signal;   means for coupling said signal generating means to said first and said second conductor means, said first conductor means being in balanced out-of-phase relation with respect to said second conductor means;   third and fourth conductor means disposed in facing relation to a side of said material opposite said first side and opposite, respectively, said first and said second conductor means, for receiving said alternating electrical signal transmitted from said first and second conductor means;   output circuit means for detecting a predetermined level of said alternating electrical signal received in said third and fourth conductor means; and   means for coupling said output circuit means to said third and fourth conductor means, said third conductor means being in balanced out-of-phase relation with repect to said fourth conductor means, whereby moisture in said moving material disposed between the oppositely facing conductor means can be detected according to signal shunting in said material, and whereby a smooth transition of output signal occurs as moist moving material enters and traverses between the oppositely disposed conductor means.   
     
     
       2. The apparatus according to claim 1 further comprising: grounded fifth conductor means in facing relation to the first side of said moving material and spaced apart laterally from and intermediate said first and second conductor means; and   grounded sixth conductor means in facing relation to the opposite side of said moving material and spaced apart laterally from and intermediate said third and fourth conductor means.   
     
     
       3. Apparatus for measuring moisture content of moving material between first and second sides of said material, said apparatus comprising: means for generating an alternating electrical signal;   first conductor means disposed in facing relation of the first side of said material for transmitting the alternating electrical signal;   second conductor means disposed in facing relation to the first side of said material in laterally spaced relation to said first conductor means for transmitting the alternating electrical signal;   means for coupling said signal generating means to said first and second conductor means, said first conductor means being in out-of-phase relation with respect to said second conductor means;   at least third conductor means disposed in facing relation to the second side of said material and opposite said first conductor means for receiving said alternating electrical signal transmitted from said first and said second conductor means; and   output circuit means coupled to said third conductor means for detecting the moisture content of said moving material disposed between said first and third conductor means according to the amount of shunting in said moving material of said transmitted alternating electrical signal, said receiving means being electrically referenced to a same level as said second conductor means.   
     
     
       4. Apparatus for measuring moisture content of moving material, said apparatus comprising: means for generating an alternating electrical signal;   a first conductive array including a first transmitting bar disposed in facing relation to a first side of said moving material,   a second transmitting bar disposed in facing relation to the first side of said moving material in spaced relation and coplanar with said first transmitting bar, and   a first receiving plate array including first and second coplanar receiving plates disposed in facing relation to a side of said moving material opposite said first side and opposite, respectively, said first and said second transmitting bars;     first means for coupling said generating means to said first and said second transmitting bars, said first transmitting bar being in balanced out-of-phase relation with said transmitting bar, said altnerating electrical signal being transmitted to said first and second receiving plates from said first and second transmitting bars;   output circuit means responsive to said alternating electrical signal coupled to said first and second receiving plates for detecting a predetermined level of said alternating electrical signal received in said first and second receiving plates; and   second means for coupling said output circuit means to said first and second receiving plates, said first receiving plate being in balanced out-of-phase relation with said second receiving plate, whereby moisture in said material disposed between the oppositely facing plates can be detected according to signal shunting in said material.   
     
     
       5. The apparatus according to claim 4 wherein said moving material traverses said apparatus simultaneously between both said transmitting bars and both said receiving plates. 
     
     
       6. The apparatus according to claim 4 wherein said moving material traverses said apparatus successively between said first bars and plates, and then said second bars and plates. 
     
     
       7. The apparatus according to claim 4 wherein said first conductor array further comprises: a first ground conductor intermediate said first and second transmitter bars; and   a second ground conductor intermediate said first and second receiving plates.   
     
     
       8. The apparatus according to claim 4 further comprising a second conductive array substantially like said first conductive array, said second conductive array being in lateral spaced relation with said first conductive array, bars and plates of said second conductive array being connected in parallel relation with the corresponding bars and plates of said first conductive array, respectively, to said first and second coupling means. 
     
     
       9. The apparatus according to claim 4 further comprising a second receiving plate array substantially similar to said first receiving plate array, said second receiving plate array being in lateral spaced relation with said first receiving plate array, the plates of said second receiving plate array being coupled to additional output circuit means. 
     
     
       10. The apparatus according to claim 4 further comprising: a second receiving plate array similar to said first mentioned receiving plate array, said second receiving plate array being in lateral spaced relation with said first receiving plate array;   additional output circuit means for detecting a predetermined level of said alternating electrical signal received in the receiving plates of said second receiving plate array; and   third means for coupling said additional output circuit means to the receiving plates of said second receiving plate array, said first receiving plate of said second receiving plate array being in balanced out-of-phase relation with said second receiving plate of said second receiving plate array, whereby moisture in said material disposed between adjacent plates of said second receiving plate array can be detected according to signal shunting in said material.   
     
     
       11. The apparatus according to claim 10 wherein said conductive array further comprises: a ground conductor intermediate said first and second transmitter bars; and   a ground plate intermediate said first and second receiving plates.